1. Field of the Invention
The present invention relates to a printing system comprised of a print data transmission device and a printing device, wherein the print data transmission device receives print data from an application program and transmits the print data to the printing device, the printing device performing a printing operation based on the received print data.
2. Description of the Related Art
Conventionally, there are two different types of printing devices. A first -type of printing device is designed for receiving, from a host computer, language expression data which describes images in a page description language (which will be referred to as PDL hereinafter). One example of the PDL is PCL, a registered trademark of Hewlett-Packard Company. The printing device of this type interprets the received language expression data and develops the language expression data into bitmap data for printing. This type of printing device will be referred to as intelligent-type printing device hereinafter.
A second type of printing device is designed to receive either compressed or uncompressed image data (bitmap data) from a host computer. When the received data is compressed, the printing device decompresses or expands the received data for printing. When the received data is not compressed, the printing device directly performs printing operation by the received data. This type of printing device will be referred to as host-based-type printing device hereinafter.
Since data for the intelligent-type printing device in expressed in language expressions, the amount of data transmitted from the host is small. This is advantageous when using an interface having a low communication speed. However, this type of printing device has to interpret the received language expressions and create corresponding bitmap image data. Accordingly, a large processing load Is placed on the printing device. As a result, the printing operation itself becomes not very fast. It takes a quite long period of time to develop language expression data into bitmap data particularly when the language expression data is described by vectors. The intelligent-type printing device may not print vector graphics within a short period of time.
On the other hand, the host-based-type printer can print received bitmap data within a short period of time. The bitmap data has been originally created by a high-speed graphics accelerator provided in the host computer. When the bitmap data is compressed, the host-based-type printer expands or decompresses the compressed bitmap data. When decompressing the bitmap data, the printer does not use any software program process such an COMDEC, but uses a hardware logic circuit to quickly decompress the compressed bitmap data. However, because the host-based-type does not use software, unlike the intelligent-type device, the host-based-type may not increase the amount of an unused area of the memory by recompressing the bitmap data. As a result, the host-based-type printing device occasionally has an insufficient memory area to form an entire image.